User:Allison K. Alix/Notebook/Thesis Research/2013/07/12

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To Do

  • Obtain UV-Vis spectra of AuNP/DNA sample as well as supernatants
  • Calculate the percentage of DNA bound to AuNP

Calculating DNA and AuNP concentrations

  • NEW* concentration of sodium citrate buffer= 268mM, must have a final concentration of 20mM in AuNP/DNA solution

20mM(500uL) = 268mM(x)

x=37.3uL sodium citrate to be added to AuNP/DNA solution

(500-37.3)/2 = 231.3uL each of DNA and AuNP to be added.

  • original AuNP concentration = 29.67nM
  • final concentration of AuNP after mixing with DNA/sodium citrate = 231.3uL(29.67.nM)= x(500uL) x = 13.73nM
  • final concentration of DNA after mixing with AuNP/sodium citrate = (13.73nM)x (75) = 1.03uM
  • original concentration of DNA needs to be = (1.03uM)(500uL) = x (231.3uL)

x = 2.226uM <-----this is the concentration prior to mixing with AuNP/sodium citrate

2.226uM(500uL) = x (250uL) x = 4.45uM <---this is the concentration prior to mixing with 250uL 100mM DTT in 4% TEA

Concentration of stock DNA = 53.1uM

53.1uM(x) = 4.45uM(250uL)

x = 21uL in 229uL 1X PBS

Preparation of 100mM Sodium Citrate Buffer

  • Original sodium citrate buffer that was prepared contained ONLY sodium citrate and HCl, not citric acid.

to prepare 100mM sodium citrate-HCl buffer:

294.1g/mol x 0.1 mol/L x 0.01L = 0.2941g in 10mL H2O

adjust pH and volume accordingly


-AuNP's still seem to be aggregating even after using freshly prepared citrate buffer. We attribute this to a few things

1) Waiting 5 minutes for the AuNP and DNA to react before adding the sodium citrate

2) The concentration of sodium citrate in solution should actually be 10mM NOT 20mM (oops...)

3) The sodium citrate buffer prepared initially only contained sodium citrate and NOT citric acid. Fresh buffer contained both.

To do on Monday, 7/15

1) Add AuNP/DNA/sodium citrate all at once and vortex immediately

2) Prepare 2 samples, one with 100mM sodium citrate buffer prepared today containing only sodium citrate and HCl and one with 268mM sodium citrate buffer prepared yesterday containing sodium citrate, citric acid, and HCl